Variable piston-stroke mechanisms

ABSTRACT

This specification covers variable piston-stroke, revolving cylinder mechanisms in which means are provided for returning the pistons to minimum cylinder-head-clearance position for any piston stroke length and in which counter-balance means are provided for minimizing piston side thrust as caused by centrifugal forces.

I United States Patent 1151 3,663,226 Biermann 14 1 May 16, 1972 54] VARIABLE PISTON-STROKE 2,232,984 2/1941 Wahlmark ,.103/3a x MECHANISMS 2,532,254 11 1950 2,545,929 3/1951 [72] Inventor: Arnold E. Blermann, Redart, Va. 23142 2 7 35 6/1955 2957421 10/1960 22 F1 d. A .22, 1969 l 1 2,964,234 l2/l960 [21] Appl. N0.: 818,212 3,046,906 7/1962 3,169,488 2/1965 [52] US. Cl ..92/57, 92/71, 46107523122 Primary Exammer-Edgar w Geoghegan [51] Int. Cl ..Folb 13/04 57 ABSTRACT [58] Field ofSearch ..92/57,71,70, 76; 103/38,

103/38 2 103/205;417/221, 222, This specification covers variable piston-stroke revolving 74/829 60/53 A cylinder mechanisms in which means are provided for returning the pistons to minimum cylinder-head-clearance position [56] References Cited for any piston stroke length and in which counter-balance means are provided for minimizing piston side thrust as caused UNITED STATES PATENTS y centrifugal 1,483,199 2/1924 Schinkez ..92/57 X 6 Claims, 5 Drawing Figures PATENTEDMAY 16 I972 SHEET 1 BF 3 INVENTOR. Arno/d 7 @[efmaruz PATENTEDHAY 16 m2 SHEET 2 BF 3 I N VEN TOR VARIABLE PISTON-STROKE MECHANISMS This invention relates to improvements in rotary engines in which the cylinders and pistons revolve and particularly to mechanisms of the type in which means are provided for adjustably changing the length of the piston stroke. Variable piston-stroke mechanisms are of advantage for compressors and motors for varying the capacity of these devices independently of speed. In particular, this invention relates to piston mechanisms which handle gases and in which the pistons must return to a position close to the cylinder head on the return stroke. Current methods of varying the capacity of compressors involve costly speed-changing devices or inefficient throttling methods. This invention provides a simple, adjustablestroke mechanism which reduces piston friction and starting loads and which simplifies the control problem.

In conventional variable-stroke hydraulic pumps it is acceptable to vary the travel on each end of its stroke. In these devices, large clearance volumes between the piston and cylinder head have little effect upon the performance because the liquid handled is essentially incompressible. For compressors and internal combustion engines the piston clearance must be held to relatively small values as stroke is varied.

In this specification piston clearance will be defined as the distance between the piston crown and the cylinder head when the piston is at its closest position to the cylinder head. The term inner piston position will designate the piston position during the cycle when the piston is at its closest position to the cylinder head. For opposed piston arrangements, these terms will refer to the adjacent piston head instead of the cylinder head.

One object of this invention is to provide a practical means for adjustably varying piston stroke at only one end of the stroke so that piston clearance at the inner position remains constant.

Another object is to provide means for making a minor change in the inner piston position as stroke is varied. This variation of clearance is required to obtain the desired compression ratio as stroke is varied, when the mechanism is applied to internal combustion engines.

A further object is to provide an efficient, compact and well-balanced mechanism capable of high speed operation.

These objectives are achieved in my invention by improving the rotary form of the piston-cylinder mechanism so that it is a practical device capable of high speed operation. In the axialtype rotary mechanism, in which the cylinders revolve and lie parallel to the axis of rotation, the centrifugal forces on the pistons and connecting rods are very high in the useful speed range. Consequently, the high piston side thrust and resulting friction and lubrication problems make the rotary engine of this type impractical in all but the smallest sizes. In this invention the centrifugal forces on the piston and linkage are reduced to negligible amounts by counter-balancing these parts on pivots supported by the rotor system. The rotor system, as defined here, includes any of the rotating parts.

The rotary mechanism, in which the cylinders revolve, has outstanding advantages when applied to variable piston-stroke machines. This mechanism is inherently balanced without resort to the use of similar mechanisms in opposition or without the use of balancing counter-weights. The balancing of a rotating crank variable stroke mechanism is very difficult because the rotating counter-weights must be varied in effect as stroke is changed. A further advantage of the rotary mechanism for variable stroke devices lies in the fact that the stroke can be varied by changing the angle or slope of a stationary cam plate. In the fixed cylinder mechanism the cam plate (wabble plate) rotates and changing the angle of this rotating plate becomes impractical.

A further advantage of the rotary mechanism lies in the fact that the pistons revolve in an almost circular path. Consequently, the high inertia forces found in the conventional reciprocating mechanism are absent. The use of rotating cylinders also lends itself to the practical use of high speed rotary valves.

My invention is capable of embodiment in many different forms, but by way of illustration I have shown only three forms thereof in the accompanying drawings in which,

FIG. 1 is a partial cross-sectional view through the center portion of one form of my invention.

FIG. 2 is a partial cross-sectional view through the device of FIG. 1 taken along line 1l.

FIG. 3 is a partial cross-sectional view through the center of a second form of my invention.

FIG. 4 is a partial sectional view taken along line 33 of FIG. 3 showing the method of mounting the carriage.

FIG. 5 is a partial cross-sectional view through a third form of my invention.

Referring to FIGS. 1 and 2, the drive shaft 6 is journaled in frame 7 in the bearings 8 and 9. Rotor 10, which is fastened to the drive shaft, embodies cylinders 11, cylinder heads 12 and cylinder ports 13. Carriage 14 is journaled for angular movement about axis B by means of the arcuate slipper 15 which is journaled in slipper support 16 of the frame and slipper cap support 17. Piston stroke-change adjusting arm 18 of carriage 14 is adjustably fastened to frame 7 by means of screw 19. The cam 20 is mounted on carriage 14. Cam follower 21 is journaled for following cam 20. Cam follower 21 is part of the rotor system. Pistons 23, in cylinders 11, are operably joined to cam follower 21 by connecting means 24 through universal joints 25 and 26. The mass of piston 23 is counter-balanced on ball 26 serving as a pivot, by the mass of counter-weight 27 of connecting means 24.

FIG. 2 shows how cam follower 21 is driven by rotor 10 by means of drive link 28 acting through universal joints 29 and 30.

In FIGS. 3 and 4, drive shaft 31 is journaled in frame 32 in bearings 33 and 34. Rotor 35 embodies cylinders 36 and guides 37. Carriage 38 is journaled for angular movement about axis B--B in frame 32 by means of shafts 40 and 41. Piston stroke-change lever 42 is fastened to shaft 40 for turning carriage 38. The inner race 43 of the ball bearing is mounted on carriage 38. The outer race of the ball bearing is part of cam 44. Pistons 45 in cylinders 36 are fastened to connecting means 46. Connecting means 46 is pivoted on rollers 47 with pins 39. Rollers 47 are operable for axial movement in guide 37. Spherical cam follower pallets 48 are seated in connecting means 46 and bear against cam 44 in slidable association. The pallets serve as cam followers. The mass of the material in the cam follower portion of connecting means 46 serves to counter-balance the mass of the piston and the supporting arm on pin 39 as a pivot. In FIG. 3 the axes of the cylinders and guides are inclined at a small angle with respect to the drive-shaft to avoid excessive sliding of the cam followers on the cam at long piston stroke settings.

In FIG. 5 drive-shaft 49 is journaled in frame 50in bearings 51 and 52. Rotor 53 embodies cylinders 54 and pistons 55. Carriage 56 is journaled for angular movement in supports 57 of frame 50 by means of pivot pins 58. Cam 59 is mounted on carriage 56. Connecting means 60 are pivoted on links 61 through pins 62. Links 61 are pivoted to rotor 53 by means of pins 63. Pistons are joined to connecting means through piston pins 64. Spherical cam follower pallets are seated in connecting means 60 and bear against cam 59 in slidable association. These pallets serve as cam followers. Counterweight 66 of connecting means 60 serves to counter-balance the mass of piston 55 on pin 62 serving as a pivot. Carriage pivot pin 58 is located adjacent to the junction of a connecting means 60 and a cam follower pallet 65 when the carriage position is set at zero stroke. Stroke is adjusted as is done in FIG. 1.

The operation of the three forms of my invention are similar. In FIG. 1, cam 20 is shown parallel to the plane of rotation and there is no movement of the pistons as the drive shaft is turned. This is the zero stroke position. In this setting all pistons remain at their closest position to the cylinder heads. This is the inner piston position. Movement of the stroke-change arm 18 to move the piston at the top of FIG. I

away from the cylinder head increases the piston stroke correspondingly. At the same time, the piston at the bottom of FIG. 1 remains at the inner position because the carriage at point B remains fixed as the angular position of the carriage is changed. Movement of the pistons causes gas to flow through the ports in the cylinder heads. The valving means required varies with the application and is not a part of this invention.

The arcuate slipper mounting 15 of carriage 14 of FIG. 1 is an important contribution to this invention. If carriage 14 was pivoted as is carriage 38 of FIG. 3, it would be too large for practical use because it would surround a portion of the path of counter-weights 27 in order to reach pivot axis BB.

This specification describes three methods of supporting the carriage; three methods of supporting and pivoting the connecting means; three methods for transmitting forces from the cam to the connecting means and two methods for driving the cam follower from the rotor. Each of these methods has certain advantages and most of them are interchangable. For example, the method of pivoting the carriage in FIG. can also be applied to FIGS. 1 and 3. Likewise, the ball bearing of FIG. 3 can be applied to FIGS. I and 5. Experience in the use of these different methods will indicate which combination offers the best compromise for the particular application involved.

The method of pivoting the carriage, as shown in FIG. 5, avoids the arcuate slipper 15 of FIG. 1 and the bulky carriage 38 of FIGS. 3 and 4. The location of the pivot, as shown in FIG. 5, however, causes the inner piston position to vary slightly as stroke is changed. For some applications this variation of inner piston position is not objectionable.

It should be observed that the use of a counter-weight for balancing out the effect of centrifugal forces on the piston is not restricted to use in a variable stroke mechanism but applies also to advantage for fixed stroke rotary mechanisms.

When equipped with a suitable rotary valve adjacent to the cylinder heads (not part of this invention) this mechanism can be used as a variable stroke compressor or as a motor for producing power from compressed gas or from steam. As a compressor. this invention is particularly adapted. to applications requiring variable capacity, such as automobile air conditioning and the supercharging of engines. This invention permits the use of smaller drive motors because it can be started without load by setting the stroke to zero.

In the foregoing applications it is necessary that the piston return to minimum clearance at the inner position in order to achieve high capacity. In this invention this requirement is achieved by locating the carriage pivot axis BB of FIG. 1 so that it passes through the center of turning of the universal joints on the cam follower when the piston is at the inner position. In other words, the turning axis of the carriage is located so that angular movement of the cam about this axis does not change the position of a piston which lies at its inner position adjacent to the cylinder head. The position of the carriage turning axis BB can also be defined as that located with respect to the cam follower such that all pistons lie adjacent to their respective cylinder heads when the piston stroke control means is set at zero stroke. In this location the turning axis of the cam and of the carriage is tangent to a circle which is concentric with respect to the periphery of the cam.

When this mechanism is applied to internal combustion engines the piston clearance must be increased a small amount, as stroke is increased, in order to hold the compression ratio constant. This can be done by placing the carriage pivot axis at a greater radius from the drive shaft than is the case with the constant piston-clearance requirement of the compressor. For simplicity in this specification, such small variations in piston clearance as may be desired will be termed the same as for constant piston clearance, unless specified otherwise.

The piston stroke-change lever can also be adjusted automatically as a function of pressure, fluid flow, rotative speed or other operating variables.

While I have described my invention in detail, I wish it to be understood that many changes may be made therein without departing from the spirit of the same.

Having thus described my inyention,lclaim:

In a mechanism for reciprocating pistons in revoking cylinders, a rotor mounted for rotation in a frame, cylinders in said rotor, pistons operable in said cylinders, a drive shaft for turning said rotor, a cam mounted on said frame, a cam follower in operable association with said cam, connecting means for operably connecting said pistons and said cam follower, said connecting means being supported on pivot means, means for revolving said pivot means about the axis of said drive shaft and counter-weight means on said connecting means such as to substantially counter-balance the mass of said pistons about said pivot means as a fulcrum.

2. In a variable piston-stroke mechanism, a frame, a drive shaft journaled in said frame, a rotor mounted for rotation in said frame, cylinders in said rotor, pistons in said cylinders, a carriage pivoted in said frame with angular adjustment means for varying piston stroke, a cam mounted on said carriage, a cam follower in operable association with said cam, connecting means connecting said pistons and said cam follower, said connecting means being supported on pivot means, means for revolving said pivot means about the axis of said drive shaft and counter-weight means on said connecting means for substantially counter-balancing the mass of said pistons about said pivot means.

3. A device as described in claim 1 in which said pivot means are supported on guide means on said rotor.

4. A device as claimed in claim 2 wherein said frame embodies an end housing and in which said carriage pivot means are mounted on said end housing.

5. A device as described in claim 2 wherein means are provided for holding the inner piston position substantially constant as piston stroke is varied.

6. A device as described in claim 2 wherein the pivot axis of said carriage is located adjacent to a junction of a connecting means and said cam follower when the piston is at the inner piston position and wherein said pivots are located outside the path of rotation of said connecting means. 

1. In a mechanism for reciprocating pistons in revolving cylinders, a rotor mounted for rotation in a frame, cylinders in said rotor, pistons operable in said cylinders, a drive shaft for turning said rotor, a cam mounted on said frame, a cam follower in operable association with said cam, connecting means for operably connecting said pistons and said cam follower, said connecting means being supported on pivot means, means for revolving said pivot means about the axis of said drive shaft and counter-weight means on said connecting means such as to substantially counter-balance the mass of said pistons about said pivot means as a fulcrum.
 2. In a variable piston-stroke mechanism, a frame, a drive shaft journaled in said frame, a rotor mounted for rotation in said frame, cylinders in said rotor, pistons in said cylinders, a carriage pivoted in said frame with angular adjustment means for varying piston stroke, a cam mounted on said carriage, a cam follower in operable association with said cam, connecting means connecting said pistons and said cam follower, said connecting means being supported on pivot means, means for revolving said pivot means about the axis of said drive shaft and counter-weight means on said connecting means for substantially counter-balancing the mass of said pistons about said pivot means.
 3. A device as described in claim 1 in which said pivot means are supported on guide means on said rotor.
 4. A device as claimed in claim 2 wherein said frame embodies an end housing and in which said carriage pivot means are mounted on said end housing.
 5. A device as described in claim 2 wherein means are provided for holding the inner piston position substantially constant as piston stroke is varied.
 6. A device as described in claim 2 wherein the pivot axis of said carriage is located adjacent to a junction of a connecting means and said cam follower when the piston is at the inner piston position and wherein said pivots are located outside the path of rotation of said connecting means. 